There are many techniques that can be used to determine an orientation of a mobile device within an environment, such as a retail, factory, warehouse, or other indoor environment, for example. Existing mobile devices, such as smart phones have several sensors (e.g. accelerometers, gyroscopes, and magnetometers) that can be utilized to calculate device motion and orientation. However, the accuracy of these sensors, and algorithms to determine orientation, vary greatly. The variation can be quite large for these sensors in some environments. For example, large metal structures, magnetic anomalies, and the like, can render magnetometer data useless in some situations.
In one solution, the orientation or motion sensors could be used to compensate each other. For example, a magnetometer may be adversely influenced by magnetic fields within the indoor environment such as those from electric motors, electronic lighting, displays, or monitors. To compensate for these magnetic anomalies, sensor data from the gyroscope and accelerometer could be used to correct for bad magnetometer data. However, the orientation sensors used in smart phones are relatively low cost, subject to drift, and do not provide a high degree of orientation accuracy.
Alternatively, inertial navigation can be used. Inertial navigation includes first determining a precise orientation of the mobile device and then tracking an orientation of the device using any one or more of the orientation or motion sensors. However, these internal reference techniques still result in errors in calculating orientation and are still subject to drift.
Accordingly, there is a need for a technique to accurately compensate an orientation of a mobile device in an indoor environment without modifying the mobile device hardware.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.